Organic el display device and method of manufacturing the same

ABSTRACT

An organic EL display device includes a first light emission layer which includes a first dopant material having a first absorbance peak in absorbance spectrum characteristics and a first host material having a first absorbance bottom on a shorter wavelength side than the first absorbance peak, the first light emission layer extending over the first to third organic EL elements and being disposed above pixel electrodes of the first to third organic EL elements, and a second light emission layer which includes a second dopant material having a second absorbance peak in absorbance spectrum characteristics and a second host material having a second absorbance bottom on a shorter wavelength side than the first absorbance peak and than the second absorbance peak, the second light emission layer extending over the first to third organic EL elements and being disposed above the first light emission layer.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is based upon and claims the benefit of priority fromprior Japanese Patent Applications No. 2008-093438, filed Mar. 31, 2008;and No. 2008-115802, filed Apr. 25, 2008, the entire contents of both ofwhich are incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an organic electroluminescence (EL)display device.

2. Description of the Related Art

In recent years, display devices using organic electroluminescence (EL)elements have vigorously been developed, by virtue of their features ofself-emission, a high response speed, a wide viewing angle, a highcontrast, small thickness and light weight.

In the organic EL element, holes are injected from a hole injectionelectrode (anode), electrons are injected from an electron injectionelectrode (cathode), and the holes and electrons are recombined in alight emitting layer, thereby producing light. In order to obtainfull-color display, it is necessary to form pixels which emit red (R)light, green (G) light and blue (B) light, respectively. It is necessaryto selectively apply light-emitting materials, which emit lights withdifferent light emission spectra, such as red, green and blue, tolight-emitting layers of organic EL elements which constitute the red,green and blue pixels. As a method for selectively applying suchlight-emitting materials, there is known a vacuum evaporation method. Inthe case of forming films of low-molecular-weight organic EL materialsby such a vacuum evaporation method, there is a method in which maskevaporation is performed independently for respective color pixels byusing a metallic fine mask having openings in association with therespective color pixels (see, e.g. Jpn. Pat. Appln. KOKAI PublicationNo. 2003-157973).

In the mask evaporation method using the metallic fine mask, however,pixels become very fine in the case where a high fineness (resolution)is required for the display device. As a result, a so-called colormixture defect, by which light-emitting materials of respective colorsare mixed, occurs frequently, and full-color display with high finenessis difficult realize.

BRIEF SUMMARY OF THE INVENTION

According to an aspect of the present invention, there is provided anorganic EL display device comprising: a pixel electrode which isdisposed in each of first to third organic EL elements having differentemission light colors; a first light emission layer which includes afirst dopant material having a first absorbance peak in absorbancespectrum characteristics and a first host material having a firstabsorbance bottom on a shorter wavelength side than the first absorbancepeak, the first light emission layer extending over the first to thirdorganic EL elements and being disposed above the pixel electrodes of thefirst to third organic EL elements; a second light emission layer whichincludes a second dopant material having a second absorbance peak inabsorbance spectrum characteristics and a second host material having asecond absorbance bottom on a shorter wavelength side than the firstabsorbance peak and than the second absorbance peak, the second lightemission layer extending over the first to third organic EL elements andbeing disposed above the first light emission layer; a third lightemission layer which includes a third dopant material and a third hostmaterial, the third light emission layer extending over the first tothird organic EL elements and being disposed above the second lightemission layer; and a counter-electrode which extends over the first tothird organic EL elements and is disposed above the third light emissionlayer.

According to another aspect of the present invention, there is providedan organic EL display device comprising: a pixel electrode which isdisposed in each of first to third organic EL elements having differentemission light colors; a first light emission layer which includes afirst dopant material having a first absorbance peak and a first hostmaterial having a first absorbance bottom, at which a normalizedabsorbance in normalized absorbance spectrum characteristics is 10% orless, on a shorter wavelength side than the first absorbance peak, thefirst light emission layer extending over the first to third organic ELelements and being disposed above the pixel electrodes of the first tothird organic EL elements; a second light emission layer which includesa second dopant material having a second absorbance peak and a secondhost material having a second absorbance bottom, at which a normalizedabsorbance in normalized absorbance spectrum characteristics is 10% orless, on a shorter wavelength side than the first absorbance peak andthan the second absorbance peak, the second light emission layerextending over the first to third organic EL elements and being disposedabove the first light emission layer; a third light emission layer whichincludes a third dopant material and a third host material, the thirdlight emission layer extending over the first to third organic ELelements and being disposed above the second light emission layer; and acounter-electrode which extends over the first to third organic ELelements and is disposed above the third light emission layer.

According to still another aspect of the present invention, there isprovided a manufacturing method of an organic EL display device,comprising: a step of forming a pixel electrode in association with eachof first to third organic EL elements having different emission lightcolors; a step of forming above the pixel electrode a first lightemission layer by using a first dopant material having a firstabsorbance peak in absorbance spectrum characteristics and a first hostmaterial having a first absorbance bottom on a shorter wavelength sidethan the first absorbance peak, the first light emission layer extendingover the first to third organic EL elements; a step of forming above thefirst light emission layer a second light emission layer by using asecond dopant material having a second absorbance peak in absorbancespectrum characteristics and a second host material having a secondabsorbance bottom on a shorter wavelength side than the first absorbancepeak and than the second absorbance peak, the second light emissionlayer extending over the first to third organic EL elements; a step offorming above the second light emission layer a third light emissionlayer by using a third dopant material and a third host material, thethird light emission layer extending over the first to third organic ELelements; and a step of forming above the third light emission layer acounter-electrode which extends over the first to third organic ELelements.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING

The accompanying drawings, which are incorporated in and constitute apart of the specification, illustrate presently preferred embodiments ofthe invention, and together with the general description given above andthe detailed description of the preferred embodiments given below, serveto explain the principles of the invention.

FIG. 1 schematically shows the structure of an organic EL display deviceaccording to an embodiment of the present invention;

FIG. 2 is a cross-sectional view which schematically shows an example ofthe structure that is adoptable in the organic EL display device shownin FIG. 1;

FIG. 3 shows one principle for controlling the emission light colors offirst to third organic EL elements;

FIG. 4 is a cross-sectional view which schematically shows the structureof the first to third organic EL elements shown in FIG. 3;

FIG. 5 is a graph showing light absorbance spectrum characteristics of afirst dopant material, a second dopant material, a first host materialand a second host material, which are adopted in the organic EL displaydevice shown in FIG. 2;

FIG. 6 is a graph showing light absorbance spectrum characteristics ofanother first host material and another second host material, which canbe adopted in the organic EL display device shown in FIG. 2;

FIG. 7 is a flow chart for describing a manufacturing method formanufacturing the first to third organic EL elements shown in FIG. 3;

FIG. 8 is a view for explaining exposure steps which are indicated by“PHOTO1 EXPOSURE” and “PHOTO2 EXPOSURE” in FIG. 7;

FIG. 9 schematically shows the structure of a polarization controlelement which generates a Z-polarization light component; and

FIG. 10 schematically shows the structure of a polarization control unitwhich includes the polarization control element shown in FIG. 9.

DETAILED DESCRIPTION OF THE INVENTION

An embodiment of the present invention will now be described in detailwith reference to the accompanying drawings. In the drawings, structuralelements having the same or similar functions are denoted by likereference numerals, and an overlapping description is omitted.

In the present embodiment, as an example of the organic EL displaydevice, a description is given of an organic EL display device of a topemission type, which adopts an active matrix driving method.

As shown in FIG. 1, this display device includes a display panel DP. Thedisplay panel DP includes an insulative substrate SUB such as a glasssubstrate.

Pixels PX1 to PX3 are arranged in an X direction in the named order, andconstitute a triplet (unit pixel) which is a minimum unit of a displaypixel. In a display region, such triplets are arranged in the Xdirection and Y direction. Specifically, in the display region, a pixelstring in which pixels PX1 are arranged in the Y direction, a pixelstring in which pixels PX2 are arranged in the Y direction and a pixelstring in which pixels PX3 are arranged in the Y direction are arrangedin the X direction in the named order, and these three pixel strings arerepeatedly arranged in the X direction.

Each of the pixels PX1 to PX3 includes a driving transistor DR,switching transistors SWa to SWc, an organic EL element OLED, and acapacitor C. In this example, the driving transistor DR and switchingtransistors SWa to SWc are p-channel thin-film transistors.

Scanning signal lines SL1 and SL2 extend in the X direction. Videosignal lines DL extend in the Y direction. The driving transistor DR,switching transistor SWa and organic EL element OLED are connected inseries in the named order between a first power supply terminal ND1 anda second power supply terminal ND2. In this example, the power supplyterminal ND1 is a high-potential power supply terminal, and the powersupply terminal ND2 is a low-potential power supply terminal. The powersupply terminal ND1 is connected to a power supply line PSL.

The gate electrode of the switching transistor SWa is connected to thescanning signal line SL1. The switching transistor SWb is connectedbetween the video signal line DL and the drain electrode of the drivingtransistor DR, and the gate electrode of the switching transistor SWb isconnected to the scanning signal line SL2. The switching transistor SWcis connected between the drain electrode and gate electrode of thedriving transistor DR, and the gate electrode of the switchingtransistor SWc is connected to the scanning signal line SL2. Thecapacitor C is connected between the gate electrode of the drivingtransistor DR and a constant potential terminal ND1′. In this example,the constant potential terminal ND1′ is connected to the power supplyterminal ND1.

The video signal line driver XDR and scanning signal line driver YDR aredisposed, for example, on the substrate SUB. Specifically, the videosignal line driver XDR and scanning signal line driver YDR areimplemented by chip on glass (COG). The video signal line driver XDR andscanning signal line driver YDR may be implemented by tape carrierpackage (TCP), instead of COG. Alternatively, the video signal linedriver XDR and scanning signal line driver YDR may be directly formed onthe substrate SUB.

The video signal lines DL are connected to the video signal line driverXDR. The video signal line driver XDR outputs current signals as videosignals to the video signal lines DL.

The scanning signal lines SL1 and SL2 are connected to the scanningsignal line driver YDR. The scanning signal line driver YDR outputsvoltage signals as first and second scanning signals to the scanningsignal lines SL1 and SL2.

When an image is to be displayed on this organic EL display device, forexample, the scanning signal lines SL2 are successively scanned.Specifically, the pixels PX1 to PX3 are selected on a row-by-row basis.In a selection period in which a certain row is selected, a writeoperation is executed in the pixels PX1 to PX3 included in this row. Ina non-selection period in which this row is not selected, a displayoperation is executed in the pixels PX1 to PX3 included in this row.

In the selection period in which the pixels PX1 to PX3 of a certain roware selected, the scanning signal line driver YDR outputs, as voltagesignals, scanning signals for opening (rendering non-conductive) theswitching transistors SWa to the scanning signal line SL1 to which thepixels PX1 to PX3 are connected. Then, the scanning signal line driverYDR outputs, as voltage signals, scanning signals for closing (renderingconductive) the switching transistors SWb and SWc to the scanning signalline SL2 to which the pixels PX1 to PX3 are connected. In this state,the video signal line driver XDR outputs, as current signals (writecurrent) I_(sig), video signals to the video signal lines DL, and sets agate-source voltage V_(gs) of the driving transistor DR at a magnitudecorresponding to the video signal I_(sig).

Subsequently, the scanning signal line driver YDR outputs, as voltagesignals, scanning signals for opening the switching transistors SWb andSWc to the scanning signal line SL2 to which the pixels PX1 to PX3 areconnected, and then outputs, as voltage signals, scanning signals forclosing the switching transistors SWa to the scanning signal line SL1 towhich the pixels PX1 to PX3 are connected. Thus, the selection periodends.

In the non-selection period following the selection period, theswitching transistors SWa are kept closed, and the switching transistorsSWb and SWc are kept opened. In the non-selection period, a drivingcurrent I_(drv), which corresponds in magnitude to the gate-sourcevoltage V_(gs) of the driving transistor DR, flows in the organic ELelement OLED. The organic EL element OLED emits light with a luminancecorresponding to the magnitude of the driving current I_(drv). In thiscase, I_(drv)≈I_(sig), and emission light corresponding to the currentsignal (write current) I_(sig) can be obtained in each pixel.

In the above-described example, the structure in which the currentsignal is written as the video signal is adopted in the pixel circuitfor driving the organic EL element OLED. Alternatively, a structure inwhich a voltage signal is written as the video signal may be adopted inthe pixel circuit. The invention is not restricted to theabove-described example. In the present embodiment, use is made ofp-channel thin-film transistors. Alternatively, n-channel thin-filmtransistors may be used, with the spirit of the invention beingunchanged. The pixel circuit is not limited to the above-describedexample, and various modes may be applicable to the pixel circuit.

FIG. 2 schematically shows the cross-sectional structure of the displaypanel DP which includes the switching transistor SWa and the organic ELelement OLED.

As shown in FIG. 2, a semiconductor layer SC of the switching transistorSWa is disposed on the substrate SUB. The semiconductor layer SC isformed of, e.g. polysilicon. In the semiconductor layer SC, a sourceregion SCS and a drain region SCD are formed, with a channel region SCCbeing interposed.

The semiconductor layer SC is coated with a gate insulation film GI. Thegate insulation film GI is formed by using, e.g. tetraethylorthosilicate (TEOS). The gate electrode G of the switching transistorSWa is disposed on the gate insulation film GI immediately above thechannel region SCC. The gate electrode G is formed of, e.g.molybdenum-tungsten (MoW).

In this example, the switching transistor SWa is a top-gate-typep-channel thin-film transistor.

The gate insulation film GI and the gate electrode G are coated with aninterlayer insulation film II. The interlayer insulation film II isformed by using, e.g. silicon oxide (SiO_(x)) which is deposited by,e.g. plasma chemical vapor deposition (CVD).

A source electrode SE and a drain electrode DE of the switchingtransistor SWa are disposed on the interlayer insulation film II. Thesource electrode SE is connected to the source region SCS of thesemiconductor layer SC. The drain electrode DE is connected to the drainregion SCD of the semiconductor layer SC.

The source electrode SE and drain electrode DE have, for example, athree-layer structure of molybdenum (Mo)/aluminum (Al)/molybdenum (Mo),and these parts can be formed by the same process. The source electrodeSE and drain electrode DE are coated with a passivation film PS. Thepassivation film PS is formed by using, e.g. silicon nitride (SiN_(x)).

Pixel electrodes PE are disposed on the passivation film PS inassociation with the pixels PX1 to PX3. Each pixel electrode PE isconnected to the drain electrode DE of the switching transistor SWa. Inthis example, the pixel electrode PE corresponds to an anode.

A partition wall PI is formed on the passivation film PS. The partitionwall PI is disposed in a lattice shape in a manner to surround theentire periphery of the pixel electrode PE. The partition wall PI may bedisposed in a stripe shape extending in the Y direction between thepixel electrodes PE. The partition wall PI is, for instance, an organicinsulation layer. The partition wall PI can be formed by using, forexample, a photolithography technique.

An organic layer ORG is disposed on each pixel electrode PE. The organiclayer ORG includes at least one continuous film which extends over thedisplay region including all pixels PX1 to PX3. Specifically, theorganic layer ORG covers the pixel electrodes PE and partition wall PI.The details will be described later.

The organic layer ORG is coated with a counter-electrode CE. In thisexample, the counter-electrode CE corresponds to a cathode. Thecounter-electrode CE is a continuous film which extends over the displayregion including all pixels PX1 to PX3. In short, the counter-electrodeCE is a common electrode which is shared by the pixels PX1 to PX3.

The pixel electrodes PE, organic layer ORG and counter-electrode CEconstitute first to third organic EL elements OLED1 to OLED3 which aredisposed in association with the pixels PX1 to PX3.

Specifically, the pixel PX1 includes the first organic EL element OLED1,the pixel PX2 includes the second organic EL element OLED2, and thepixel PX3 includes the third organic EL element OLED3. Although FIG. 2shows one first organic EL element OLED1 of the pixel PX1, one secondorganic EL element OLED2 of the pixel PX2 and one third organic ELelement OLED3 of the pixel PX3, these organic EL elements OLED1, OLED2and OLED3 are repeatedly disposed in the X direction. Specifically,another first organic EL element OLED1 is disposed adjacent to the thirdorganic EL element OLED3 that is shown on the right side part of FIG. 2.Similarly, another third organic EL element OLED3 is disposed adjacentto the first organic EL element OLED1 that is shown on the left sidepart of FIG. 2.

The partition wall PI is disposed between, and divides, the firstorganic EL element OLED1 and second organic EL element OLED2. Inaddition, the partition wall PI is disposed between, and divides, thesecond organic EL element OLED2 and third organic EL element OLED3.Further, the partition wall PI is disposed between, and divides, thethird organic EL element OLED3 and first organic EL element OLED1.

The sealing of the first to third organic EL elements OLED1 to OLED3 maybe effected by bonding a sealing glass substrate SUB2, to which adesiccant (not shown) is attached, by means of a sealant which isapplied to the periphery of the display region. Alternatively, thesealing of the first to third organic EL elements OLED1 to OLED3 may beeffected by bonding the sealing glass substrate SUB2 by means of fritglass (frit sealing), or by filling an organic resin layer between thesealing glass substrate SUB2 and the organic EL element OLED (solidsealing). In the case of the frit sealing, the desiccant may bedispensed with. In the case of the solid sealing, an insulation film ofan inorganic material may be interposed between the organic resin layerand the counter-electrode CE.

In the present embodiment, the first to third organic EL elements OLED1to OLED3 are configured to have different emission light colors. In thisexample, the emission light color of the first organic EL element OLED1is red, the emission light color of the second organic EL element OLED2is green, and the emission light color of the third organic EL elementOLED3 is blue.

In general, the color of light in the range of wavelengths of 400 nm to435 nm is defined as purple; the color of light in the range ofwavelengths of 435 nm to 480 nm is defined as blue; the color of lightin the range of wavelengths of 480 nm to 490 nm is defined as greenishblue; the color of light in the range of wavelengths of 490 nm to 500 nmis defined as bluish green; the color of light in the range ofwavelengths of 500 nm to 560 nm is defined as green; the color of lightin the range of wavelengths of 560 nm to 580 nm is defined as yellowishgreen; the color of light in the range of wavelengths of 580 nm to 595nm is defined as yellow; the color of light in the range of wavelengthsof 595 nm to 610 nm is defined as orange; the color of light in therange of wavelengths of 610 nm to 750 nm is defined as red; and thecolor of light in the range of wavelengths of 750 nm to 800 nm isdefined as purplish red. In this example, the color of light with amajor wavelength in the range of wavelengths of 400 nm to 490 nm isdefined as blue; the color of light with a major wavelength, which isgreater than 490 nm and less than 595 nm, is defined as green; and thecolor of light with a major wavelength in the range of wavelengths of595 nm to 800 nm is defined as red.

FIG. 3 schematically shows the structure of each of the first to thirdorganic EL elements OLED1 to OLED3. As shown in FIG. 3, each of thefirst organic EL element OLED1 of the pixel PX1, the second organic ELelement OLED2 of the pixel PX2 and the third organic EL element OLED3 ofthe pixel PX3 is disposed on the passivation film PS. Each of the firstto third organic EL elements OLED1 to OLED3 includes a pixel electrodePE, a counter-electrode CE that is opposed to the pixel electrode PE,and an organic layer ORG that is interposed between the pixel electrodePE and counter-electrode CE.

The first to third organic EL elements OLED1 to OLED3 are structured asdescribed below.

Specifically, the pixel electrode PE is disposed on the passivation filmPS. The organic layer ORG is disposed on the pixel electrode PE. Theorganic layer ORG includes a red light emission layer EML1 which is afirst light emission layer disposed on the pixel electrode PE, a greenlight emission layer EML2 which is a second light emission layerdisposed on the red light emission layer EML1, and a blue light emissionlayer EML3 which is a third light emission layer disposed on the greenlight emission layer EML2. The counter-electrode CE is disposed on theorganic layer ORG.

The red light emission layer EML1 is formed of a mixture of a first hostmaterial HM1 and a first dopant material EM1 whose emission light coloris red. The first dopant material EM1 is a red light-emitting materialwhich is formed of a luminescent organic compound or composition havinga central light emission wavelength in red wavelengths. The red lightemission layer EML1 is formed, for example, by using 9,9-bis(9-phenyl-9H-carbazole) fluorine (abbreviation: FL-2CBP) as the firsthost material HM1, and4-(dicyanomethylene)-2-methyl-6-(julolidin-4-yl-vinyl)-4H-pyran (DCM2)as the first dopant material EM1.

The characteristics which the first host material HM1 is required tohave are such absorbance spectrum characteristics as to have anabsorbance bottom on a shorter wavelength side than an absorbance peakin absorbance spectrum characteristics of the first dopant material EM1.

The green light emission layer EML2 is formed of a mixture of a secondhost material HM2 and a second dopant material EM2 whose emission lightcolor is green. The second dopant material EM2 is a green light-emittingmaterial which is formed of a luminescent organic compound orcomposition having a central light emission wavelength in greenwavelengths. The green light emission layer EML2 is formed, for example,by using FL-2CBP as the second host material HM2, andtris(8-hydroxyquinolato)aluminum (abbreviation: Alq₃) as the seconddopant material EM2.

The characteristics which the second host material HM2 is required tohave are such absorbance spectrum characteristics as to have anabsorbance bottom on a shorter wavelength side than absorbance peaks inabsorbance spectrum characteristics of the first dopant material EM1 andsecond dopant material EM2.

The blue light emission layer EML3 is formed of a mixture of a thirdhost material HM3 and a third dopant material EM3 whose emission lightcolor is blue. The third dopant material EM3 is a blue light-emittingmaterial which is formed of a luminescent organic compound orcomposition having a central light emission wavelength in bluewavelengths. The blue light emission layer EML3 is formed, for example,by using 4,4′-bis(2,2′-diphenyl-ethen-1-yl)-diphenyl (BPVBI) as thethird host material, and perylene as the third dopant material EM3.

As the first host material HM1 and second host material HM2, use may bemade of 1,3,5-tris (carbazole-9-yl) benzene (abbreviation: TCP), asidefrom the above-described examples. Other materials may also be used.

Materials, other than the above-described examples, may be used as thefirst dopant material EM1, second dopant material EM2 and third dopantmaterial EM3. At least one of the first dopant material EM1, seconddopant material EM2 and third dopant material EM3 may be aphosphorescent material.

A description is given of the principle for controlling the emissionlight colors in the first to third organic EL elements OLED1 to OLED3.

The band gap of the first dopant material EM1 is smaller than the bandgap of each of the second dopant material EM2 and third dopant materialEM3. The band gap of the second dopant material EM2 is smaller than theband gap of the third dopant material EM3. The band gap corresponds toan energy difference between a lowest unoccupied molecular orbital(LUMO) and a highest occupied molecular orbital (HOMO).

In the first organic EL element OLED1, since the band gap of the firstdopant material EM1 that is included in the red light emission layerEML1 is smallest, no energy transition occurs to other layers.Therefore, the first organic EL element OLED1 emits red light, andneither the green light emission layer EML2 nor blue light emissionlayer EML3 emits light.

In the second organic EL element OLED2, the first dopant material EM1 ofthe red light emission layer EML1 is in an optical quenching state. Theoptical quenching state refers to a state in which the dopant materialabsorbs ultraviolet and thus decomposition, polymerization or a changein molecular structure occurs in the dopant material, and, as a result,light emission does not occur or light emission hardly occurs. In thered light emission layer EML1 of the second organic EL element OLED2,the first dopant material EM1 emits no light. Even if the first dopantmaterial EM1 is in the optical quenching state, the band gap in the redlight emission layer EML1 is substantially equal to or less than theband gap prior to the optical quenching.

At this time, in the red light emission layer EML1 of the second organicEL element OLED2, the hole injectability or hole transportability of thered light emission layer EML1 increases by the ultraviolet irradiationfor the optical quenching of the first dopant material EM1, and the holemobility becomes higher than in the state prior to the ultravioletradiation. Hence, in the second organic EL element OLED2, the balancebetween electrons and holes varies, and the light emission positionshifts to the green light emission layer EML2. Therefore, the secondorganic EL element OLED2 emits green light, and the blue light emissionlayer EML3 emits no light.

In the third organic EL element OLED3, the first dopant material EM1 ofthe red light emission layer EML1 and the second dopant material EM2 ofthe green light emission layer EML2 are in the optical quenching state.In the red light emission layer EML1 of the third organic EL elementOLED3, the first dopant material EM1 emits no light. In addition, in thegreen light emission layer EML2 of the third organic EL element OLED3,the second dopant material EM2 emits no light. Even if the first dopantmaterial EM1 is in the optical quenching state, the band gap in the redlight emission layer EML1 is substantially equal to or less than theband gap prior to the optical quenching. In addition, even if the seconddopant material EM2 is in the optical quenching state, the band gap inthe green light emission layer EML2 is substantially equal to or lessthan the band gap prior to the optical quenching.

At this time, in the red light emission layer EML1 of the third organicEL element OLED3, like the second organic EL element OLED2, the holeinjectability or hole transportability increases. Similarly, in thegreen light emission layer EML2 of the third organic EL element OLED3,the hole injectability or hole transportability of the green lightemission layer EML2 increases by the ultraviolet irradiation for theoptical quenching of the second dopant material EM2, and the holemobility becomes higher than in the state prior to the ultravioletradiation. Hence, in the third organic EL element OLED3, the balancebetween electrons and holes varies, and the light emission positionshifts to the blue light emission layer EML3. Therefore, the thirdorganic EL element OLED3 emits blue light.

FIG. 4 schematically shows the cross-sectional structure of the first tothird organic EL elements OLED1 to OLED3. The cross-sectional structureshown in FIG. 4 does not include the switching transistor.

As shown in FIG. 4, the gate insulation film GI, interlayer insulationfilm II and passivation film PS are interposed between the substrate SUBand each of the first to third organic EL elements OLED1 to OLED3. Eachpixel electrode PE is disposed on the passivation film PS.

The red light emission layer EML1 is disposed on each of the pixelelectrodes PE of the first to third organic EL elements OLED1 to OLED3.The red light emission layer EML1 extends over the first to thirdorganic EL elements OLED1 to OLED3.

Specifically, the red light emission layer EML1 is a continuous filmspreading over the display region, and is disposed common to the firstto third organic EL elements OLED1 to OLED3. In addition, the red lightemission layer EML1 is disposed on each of the partition walls PI whichare disposed between the first organic EL element OLED1 and secondorganic EL element OLED2, between the second organic EL element OLED2and third organic EL element OLED3, and between the third organic ELelement OLED3 and first organic EL element OLED1.

The green light emission layer EML2 extends over the first to thirdorganic EL elements OLED1 to OLED3, and is disposed on the red lightemission layer EML1. Specifically, the green light emission layer EML2is a continuous film spreading over the display region.

The blue light emission layer EML3 extends over the first to thirdorganic EL elements OLED1 to OLED3, and is disposed on the green lightemission layer EML2. Specifically, the blue light emission layer EML3 isa continuous film spreading over the display region.

The counter-electrode CE extends over the first to third organic ELelements OLED1 to OLED3, and is disposed on the blue light emissionlayer EML3. Specifically, the counter-electrode CE is a continuous filmspreading over the display region.

The first to third organic EL elements OLED1 to OLED3 are sealed byusing the sealing glass substrate SUB2.

FIG. 5 shows normalized light absorbance spectrum characteristics ofDCM2 that is the first dopant material EM1, Alq₃ that is the seconddopant material EM2, and FL-2CBP that is the first host material HM1 andthe second host material HM2.

DCM2 that is the first dopant material EM1 has absorbance spectrumcharacteristics which are indicated by (a) in FIG. 5, and has anabsorbance peak in the vicinity of the wavelength of 500 nm. Alq₃ thatis the second dopant material EM2 has absorbance spectrumcharacteristics which are indicated by (b) in FIG. 5, and has anabsorbance peak in the vicinity of the wavelength of 400 nm.

FL-2CBP that is the first host material HM1 and the second host materialHM2 has absorbance spectrum characteristics which are indicated by (c)in FIG. 5, and has an absorbance peak in the vicinity of the wavelengthof 300 nm and a substantial absorbance bottom between the wavelength of350 nm and the wavelength of 400 nm. In the normalized absorbancespectrum characteristics, the absorbance bottom corresponds to a regionwhere the normalized absorbance decreases to a minimum. In the casewhere the absorbance spectrum characteristics have substantially an Lshape curve, as in the example shown in FIG. 5, that part of the bottomside of the L shape curve, which is located on the shortest wavelengthside, is referred to as “absorbance bottom”. Although not shown, in thecase where the absorbance spectrum characteristics have substantially aU shape curve, that part of the U shape curve, which has a lowestnormalized absorbance, is referred to as “absorbance bottom”. In thenormalized absorbance spectrum characteristics, the normalizedabsorbance is 10% or less at the absorbance bottom.

As regards the FL-2CBP, on the shorter wavelength side than thewavelength of 350 nm, the normalized absorbance is 10% or more. Theabsorbance bottom appears in the vicinity of the wavelength of 360 nm,and the normalized absorbance is generally 10% or less on the longerwavelength side. In short, the absorbance bottom of the FL-2CBP occurson the shorter wavelength side than the absorbance peaks of the firstdopant material EM1 and second dopant material EM2.

FIG. 6 shows normalized light absorbance spectrum characteristics ofDCM2 that is the first dopant material EM1, Alq₃ that is the seconddopant material EM2, and TCP that is applicable as the first hostmaterial HM1 and the second host material HM2.

In FIG. 6, (a) and (b) indicate absorbance spectrum characteristics ofDCM2 and Alq₃. TCP has absorbance spectrum characteristics which areindicated by (d) in FIG. 6, and has an absorbance peak in the vicinityof the wavelength of 300 nm and a substantial absorbance bottom betweenthe wavelength of 350 nm and the wavelength of 400 nm. As regards theTCP, on the shorter wavelength side than the wavelength of 350 nm, thenormalized absorbance is 10% or more. The absorbance bottom appears inthe vicinity of the wavelength of 355 nm, and the normalized absorbanceis generally 10% or less on the longer wavelength side. In short, theabsorbance bottom of the TCP occurs on the shorter wavelength side thanthe absorbance peaks of the first dopant material EM1 and second dopantmaterial EM2.

In FIG. 5 and FIG. 6, (a) and (b) indicate the absorbance spectrumcharacteristics in the state in which no optical quenching occurs in thefirst dopant material EM1 and second dopant material EM2. In theabsorbance spectrum characteristics in the state in which the opticalquenching occurs in the first dopant material EM1 and second dopantmaterial EM2, the absorbance peaks may slightly become lower than in thestate before the optical quenching, or the wavelengths at which theabsorbance peaks occur may slightly vary. However, the absorption peaksdo not greatly vary, compared to the state before the optical quenching.In particular, the wavelengths at which the absorbance peaks occur donot shift to the shorter wavelength side than the absorbance bottom ofthe first host material HM1 and second host material HM2.

Next, referring to a flow chart of FIG. 7, a description is given of anexample of a manufacturing method of the first to third organic ELelements OLED1 to OLED3.

To start with, in an array process, a pixel electrode PE is formed on apassivation film.

Then, in an EL process, a red light emission layer EML1 including afirst dopant material EM1 is formed by a vacuum evaporation method byusing a rough mask in which an opening corresponding to the displayregion is formed. In FIG. 7, this step is indicated by “EML1EVAPORATION”.

Then, regions, which correspond to the pixel PX2 in which the secondorganic EL element OLED2 is formed and the pixel PX3 in which the thirdorganic EL element OLED3 is formed, are irradiated with light in a rangeof wavelengths of about 355 to 800 nm with an intensity in a range of0.001 to 1.0 mW·mm⁻²·nm⁻¹. In this example, the intensity of irradiationlight is set at about 0.1 mW·mm⁻²·nm⁻¹. In FIG. 7, this step isindicated by “PHOTO1 EXPOSURE”.

In the exposure step indicated by “PHOTO1 EXPOSURE”, in the pixels PX2and PX3 which are irradiated with light with the wavelengths of about355 to 800 nm, the first dopant material EM1 in the red light emissionlayer EML1 absorbs the irradiation light since the first dopant materialEM1 has an absorbance peak in the vicinity of 500 nm. Thereby, theoptical quenching occurs in the first dopant material EM1 due todecomposition, polymerization or a change in molecular structure. On theother hand, in the pixels PX2 and PX3, the normalized absorbance of thefirst host material HM1 in the wavelength range of irradiation light isrelatively low and is 10% or less. Thus, even if the first host materialHM1 absorbs the irradiation light, there occurs no decomposition,polymerization or change in molecular structure.

Subsequently, a green light emission layer EML2 including a seconddopant material EM2 is formed by a vacuum evaporation method by using arough mask in which an opening corresponding to the display region isformed. In FIG. 7, this step is indicated by “EML2 EVAPORATION”.

Then, the region, which corresponds to the pixel PX3 is irradiated withlight in a range of wavelengths of about 355 to 800 nm with an intensityin a range of 0.001 to 1.0 mW·mm⁻²·nm⁻¹. In this example, the intensityof irradiation light is set at about 0.1 mW·mm⁻²·nm⁻¹. In FIG. 7, thisstep is indicated by “PHOTO2 EXPOSURE”. In the meantime, ultravioletlights with different wavelengths may be radiated in the “PHOTO1EXPOSURE” and “PHOTO2 EXPOSURE”.

In the exposure step indicated by “PHOTO2 EXPOSURE”, in the pixel PX3which is irradiated with light with the wavelengths of about 355 to 800nm, the second dopant material EM2 in the green light emission layerEML2 absorbs the irradiation light since the second dopant material EM2has an absorbance peak in the vicinity of 400 nm. Thereby, the opticalquenching occurs in the second dopant material EM2 due to decomposition,polymerization or a change in molecular structure. On the other hand, inthe pixel PX3, the normalized absorbance of the second host material HM2in the wavelength range of irradiation light is relatively low and is10% or less. Thus, even if the second host material HM2 absorbs theirradiation light, there occurs no decomposition, polymerization orchange in molecular structure.

Subsequently, a blue light emission layer EML3 including a third dopantmaterial EM3 is formed on the green light emission layer EML2 by avacuum evaporation method by using a rough mask in which an openingcorresponding to the display region is formed. In FIG. 7, this step isindicated by “EML3 EVAPORATION”.

Then, a counter-electrode CE is formed on the blue light emission layerEML3. In FIG. 7, this step is indicated by “CE EVAPORATION”.

Thereafter, a step of sealing by the sealing glass substrate SUB2 isperformed.

As shown in FIG. 8, in the exposure step indicated by “PHOTO1”, light isradiated by using a photomask MASK1 which shields the pixel PX1 fromlight and has an opening facing the pixels PX2 and PX3. Thereby, in thered light emission layer EML1 that is formed in the preceding step, thefirst dopant material EM1 of the red light emission layer EML1 that isformed in the pixels PX2 and PX3 absorbs light and transitions into anoptical quenching state.

In the subsequent exposure step indicated by “PHOTO2”, light is radiatedby using a photomask MASK2 which shields the pixel PX1 and pixel PX2from light and has an opening facing the pixel PX3. Thereby, in thegreen light emission layer EML2 that is formed in the preceding step,the second dopant material EM2 of the green light emission layer EML2that is formed in the pixel PX3 absorbs light and transitions into anoptical quenching state.

As described above, the red light emission layer EML1, green lightemission layer EML2 and blue light emission layer EML3 are thecontinuous films extending over the first to third organic EL elementsOLED1 to OLED3. Similarly, the counter-electrode CE is the continuousfilm extending over the first to third organic EL elements OLED1 toOLED3. Thus, when these films are formed by the evaporation method, afine mask in which a fine opening is formed is needless, and themanufacturing cost of the mask can be reduced. In addition, when thesefilms are formed, the amount of material deposited on the maskdecreases, and the efficiency of use of the material of the films isenhanced. Moreover, since there is no need to selectively apply thelight-emitting materials, a defect of color mixture can be prevented.

Besides, the second organic EL element OLED2 emits green light since thefirst dopant material EM1 of the red light emission layer EML1 is in theoptical quenching state. The third organic EL element OLED3 emits bluelight since the first dopant material EM1 of the red light emissionlayer EML1 and the second dopant material EM2 of the green lightemission layer EML2 are in the optical quenching state. Accordingly,full-color display with high fineness can be realized.

When the optical quenching is effected in the first dopant material EM1of the red light emission layer EML1 and the second dopant material EM2of the green light emission layer EML2, the productivity of the organicEL display device can be more improved as the exposure time in thePHOTO1 exposure and PHOTO2 exposure is shorter.

As means for shortening the exposure time, there is a method ofincreasing the intensity of exposure. The radiation light wavelength ofa high-pressure mercury lamp, which is a light source of a generalexposure device, is in the range of 200 to 600 nm, and the peakwavelength, at which the emission light intensity takes a maximum value,is 365 nm in the emission light spectrum characteristics.

If all wavelengths of the radiation light of the high-pressure mercurylamp are utilized for exposure, the radiation intensity increases, butthe wavelengths include wavelengths of light which is absorbed by notonly the first dopant material EM1 and second dopant material EM2, butalso the first host material HM1 and second host material HM2.Consequently, there may possibly occur decomposition, polymerization ora change in molecular structure in the first host material HM1 andsecond host material HM2.

It is thinkable to radiate light of wavelengths, which is hardlyabsorbed by the first host material HM1 and second host material HM2 butis absorbed by only the first host material HM1 and second host materialHM2. In such a case, however, an optical element for selectingwavelengths is needed. In addition, at the time of exposure, theradiation intensity decreases due to the limitation of radiationwavelengths, and also the radiation intensity at the time when theradiation light passes through the optical element decreases due to,e.g. absorption of light by the optical element itself. Consequently,since the exposure intensity decreases and the exposure time increases,the productivity may possibly deteriorate.

No decomposition, polymerization or change in molecular structure iscaused in the first host material HM1 and second host material HM2 byradiating light that has wavelengths, which are longer than theabsorbance bottoms in the absorbance spectrum characteristics of thefirst host material HM1 included in the red light emission layer EML1and the second host material HM2 included in the green light emissionlayer EML2, as the wavelengths of light for use in the exposure steps of“PHOTO1 EXPOSURE” and “PHOTO2 EXPOSURE”.

On the other hand, the first dopant material EM1 and second dopantmaterial EM2, which are to be set in the optical quenching state, haveabsorption peaks in the absorbance spectrum characteristics on thelonger wavelength side than the absorbance bottom of the first hostmaterial HM1 and second host material HM2. In the exposure steps of“PHOTO1 EXPOSURE” and “PHOTO2 EXPOSURE”, light is radiated which has thewavelengths including wavelengths in the vicinity of the absorbancebottom of the first host material HM1 and second host material HM2, andwavelengths longer than these wavelengths in the vicinity of theabsorbance bottom. Specifically, as the exposure wavelengths in eachexposure step, use can be made of the wavelengths in the range longerthan the wavelengths in the ultraviolet range (200 to 400 nm) at whichthe normalized absorbance of the first host material HM1 and second hostmaterial HM2 is 10% or less, and all wavelengths in the visible lightrange. This wavelength range includes the peak wavelength of thehigh-pressure mercury lamp that is the light source. Therefore, theexposure intensity can be kept at a high level, and the productivity canbe improved by the decrease in exposure time.

A description is given of examples of variations of elements, which canbe adopted in the first to third organic EL elements OLED1 to OLED3 inthe present embodiment.

For example, the organic layer ORG of each of the first to third organicEL elements OLED1 to OLED3 may include a hole injection layer and a holetransport layer on the pixel electrode side. In this case, the holeinjection layer is disposed on the pixel electrode PE, and the holetransport layer is disposed on the hole injection layer. In addition,the organic layer ORG of each of the first to third organic EL elementsOLED1 to OLED3 may include an electron injection layer and an electrontransport layer on the counter-electrode side. In this case, theelectron transport layer is disposed on the blue light emission layerEML3, and the electron injection layer is disposed on the electrontransport layer. The hole injection layer, hole transport layer,electron injection layer and electron transport layer can be formed by avacuum evaporation method by using a rough mask.

The pixel electrode PE of each of the first to third organic EL elementsOLED1 to OLED3 may have a two-layer structure in which a reflectivelayer and a transmissive layer are stacked, or may have a singletransmissive layer structure or a single reflective layer structure. Thereflective layer can be formed of a light-reflective, electricallyconductive material such as silver (Ag) or aluminum (Al). Thelight-transmissive layer can be formed of a light-transmissive,electrically conductive material such as indium tin oxide (ITO) orindium zinc oxide (IZO). In the case where the pixel electrode PE hasthe two-layer structure comprising the reflective layer and transmissivelayer, the reflective layer is disposed on the passivation film PS, andthe transmissive layer is disposed on the reflective layer.

The counter-electrode CE may have a two-layer structure in which asemi-transmissive layer and a transmissive layer are stacked, or mayhave a single transmissive layer structure or a single semi-transmissivelayer structure. The semi-transmissive layer can be formed of anelectrically conductive material such as magnesium or silver. Thetransmissive layer can be formed of a light-transmissive, electricallyconductive material such as ITO or IZO.

The first to third organic EL elements OLED1 to OLED3 may adopt atop-emission-type structure in which emission light is extracted fromthe counter-electrode side. In this case, the pixel electrode PE of eachof the first to third organic EL elements OLED1 to OLED3 includes atleast a reflective layer.

The first to third organic EL elements OLED1 to OLED3 may adopt amicro-cavity structure which comprises a pixel electrode PE having areflective layer, and a counter-electrode CE having a semi-transmissivelayer.

In the case where the micro-cavity structure is adopted, alight-transmissive thin film, for instance, silicon oxynitride (SiON) orITO, may be disposed on the counter-electrode CE. Such a thin film isusable as a protection film for protecting the first to third organic ELelements OLED1 to OLED3, and is also usable as an optical matching layerfor adjusting the optical path length for optimizing opticalinterference. Moreover, a light-transmissive insulation film, forinstance, silicon nitride (SiN), may be disposed between the reflectivelayer of the pixel electrode PE and the semi-transmissive layer of thecounter-electrode CE. Such an insulation film is usable as an adjustinglayer for adjusting an optical interference condition. The optical pathlength of such an adjusting layer is set at a least common multiple of ¼of the wavelength of emission light of each of the first to thirdorganic EL elements OLED1 to OLED3. Such an adjusting layer may bedisposed only in the first organic EL element OLED1 and the secondorganic EL element OLED2.

Of the first to third organic EL elements OLED1 to OLED3, at least thefirst organic EL element OLED1 and the second organic EL element OLED2may include an irregular scattering layer which is disposed between thepixel electrode PE and the passivation film PS.

In the present embodiment, the description has been given of the case inwhich the hole injectability or hole transportability in the red lightemission layer EML1 and green light emission layer EML2 is increased bythe ultraviolet irradiation for causing optical quenching in the firstdopant material EM1 of the red light emission layer EML1 and the seconddopant material EM2 of the green light emission layer EML2.Alternatively, the same advantageous effect can be obtained in the casein which the hole injectability or hole transportability in the redlight emission layer EML1 and green light emission layer EML2 isdecreased by the ultraviolet irradiation.

A description is given of examples of variations which can be adopted inthe manufacturing method of the first to third organic EL elements OLED1to OLED3.

The exposure step that is indicated by “PHOTO1 EXPOSURE” may beperformed at any timing, if the timing is after the step of forming thered light emission layer EML1, which is indicated by “EML1 EVAPORATION”.For example, the exposure step indicated by “PHOTO1 EXPOSURE” may beperformed after the step of forming the green light emission layer EML2which is indicated by “EML2 EVAPORATION”, or after the step of formingthe blue light emission layer EML3 which is indicated by “EML3EVAPORATION”, or after the step of forming the counter-electrode CEwhich is indicated by “CE EVAPORATION”.

The exposure step that is indicated by “PHOTO2 EXPOSURE” may beperformed at any timing, if the timing is after the step of forming thegreen light emission layer EML2, which is indicated by “EML2EVAPORATION”. For example, the exposure step indicated by “PHOTO2EXPOSURE” may be performed after the step of forming the blue lightemission layer EML3 which is indicated by “EML3 EVAPORATION”, or afterthe step of forming the counter-electrode CE which is indicated by “CEEVAPORATION”.

In the case of the structure in which the organic layer ORG of each ofthe first to third organic EL elements OLED1 to OLED3 includes the holetransport layer, a step of forming the hole transport layer and a stepof exposing the hole transport layer may be added prior to the step offorming the red light emission layer EML1 which is indicated by “EML1EVAPORATION”.

In the case of the structure in which the organic layer ORG of each ofthe first to third organic EL elements OLED1 to OLED3 includes theelectron transport layer, a step of forming the electron transport layerand a step of exposing the electron transport layer may be added afterthe step of forming the blue light emission layer EML3 which isindicated by “EML3 EVAPORATION”.

In the present embodiment, the description has been given of the case inwhich two exposure steps indicated by “PHOTO1 EXPOSURE” and “PHOTO2EXPOSURE” are performed. Alternatively, by making use of a halftonemask, the optical quenching may be caused to occur in the first dopantmaterial EM1 and second dopant material EM2 by a single exposure step.This halftone exposure step may be performed at any timing, if thetiming is after the step of forming the green light emission layer EML2.The halftone mask, which is used in this case, has differenttransmittances corresponding to the respective regions where the firstto third organic EL elements OLED1 to OLED3 are to be formed.Specifically, the transmittance corresponding to the region where thethird organic EL element OLED3 is to be formed is higher than thetransmittance corresponding to the region where the second organic ELelement OLED2 is to be formed. The transmittance corresponding to theregion where the second organic EL element OLED2 is to be formed ishigher than the transmittance corresponding to the region where thefirst organic EL element OLED1 is to be formed. Thereby, the exposurestep is simplified, and the productivity is improved.

In the exposure steps indicated by “PHOTO1 EXPOSURE” and “PHOTO2EXPOSURE”, it is preferable that the oxygen concentration in theexposure device be set at 20 ppm. Under this condition of the oxygenconcentration, the optical quenching in the first dopant material EM1and second dopant material EM2 is promoted.

For example, FL-2CBP is used as the host material,tri(2-phenylpyridine)iridium (III) (abbreviation: Ir(ppy)3) is used asthe dopant material, and a thin film with a thickness of 30 nm and adopant concentration of 8% is formed on a glass substrate by a vacuumevaporation method. Light of 355 nm or more was radiated for 10 minuteson this formed thin film by using a mercury xenon lamp light source,both in the environment in which the oxygen concentration is 1 ppm orless and the environment in which the oxygen concentration is 20 ppm.

Before and after the light radiation, the photoluminescence intensity(PL intensity) was compared by a photoluminescence method. In the casewhere the PL intensity before the light radiation is assumed to be 100%,the PL intensity decreased to 49% after the light radiation in theenvironment in which the oxygen concentration is 1 ppm, and the PLintensity decreased to 38% after the light radiation in the environmentin which the oxygen concentration is 20 ppm.

As described above, in the case of irradiation of light with wavelengthsof 355 nm or more, a variation, such as decomposition of FL-2CBP that isthe host material is suppressed, and thus it can be assumed that thedecrease in PL intensity by the light radiation occurs due to theoptical quenching of the dopant material. Therefore, in the exposuresteps indicated by “PHOTO1 EXPOSURE” and “PHOTO2 EXPOSURE”, byperforming the exposure in the environment in which the oxygenconcentration is 20 ppm or more, the optical quenching of the dopantmaterial can be effected in a shorter time, and the productivity can beenhanced.

Next, a description is given of an example of a polarization controlelement which is applicable to the exposure steps indicated by “PHOTO1EXPOSURE” and “PHOTO2 EXPOSURE”.

FIG. 9 shows a structure example of a polarization control element 100.In FIG. 9, the direction of travel of light is set to be a Z direction,and directions that are perpendicular to each other in a planeperpendicular to the Z direction are set to be an X direction and a Ydirection. The polarization control element 100 is constructed bycombining a polarization modulation element 110 which generates, fromradiation light RL from a light source, linearly polarized light rays ina plurality of different directions in the X-Y plane, and a lens 120which collects the linearly polarized light rays coming out of thepolarization modulation element 110.

The polarization modulation element 110 can be composed of a liquidcrystal panel which is configured to hold a liquid crystal layer betweena pair of substrates. In particular, a liquid crystal panel of a mode,in which linearly polarized light rays in a plurality of differentdirections can be produced from light passing through a liquid crystaldisplay panel, for instance, a twisted nematic mode or an in-planeswitching mode, is suitable.

The polarization modulation element 110 includes a first quadrant 111, asecond quadrant 112, a third quadrant 113 and a fourth quadrant 114. Thepolarization modulation element 110 is configured such that the phasesof transmissive light rays, which pass through the first to fourthquadrants, are different. Thus, the directions of optical axes 111P to114P of the light rays, which pass through the first to fourth quadrants111 to 114, are different in the X-Y plane. Although FIG. 9 shows theexample in which the polarization modulation element 110 includes thefour quadrants 111 to 114, it is preferable that the polarizationmodulation element 110 have at least four quadrant regions for varyingthe polarization state of the radiation light RL from the light source.

An example of the method of forming the quadrant regions in which thepolarization axes of transmissive light rays are different in the liquidcrystal panel, which constitutes the polarization modulation element110, is a method in which the combination of the “tilt angle in arubbing treatment process” and the “application voltage for controllingliquid crystal alignment” is varied among the quadrant regions.

In the polarization control element 100 having the above-describedstructure, radiation light RL from the light source first enters thepolarization modulation element 110. Transmissive light including anX-polarization light component and a Y-polarization light component,which have different phases, emerges from each of the first to fourthquadrant regions 111 to 114. A transmissive light ray group TLG, whichcomprises transmissive light rays from the first to fourth quadrantregions 111 to 114, includes linearly polarized light rays PL1 to PL4which are parallel to polarization axes 111P to 114P of the first tofourth quadrant regions 111 to 114. Specifically, the transmissive lightemerging from the first quadrant region 111 is the linearly polarizedlight PL1, the transmissive light emerging from the second quadrantregion 112 is the linearly polarized light PL2, the transmissive lightemerging from the third quadrant region 113 is the linearly polarizedlight PL3, and the transmissive light emerging from the fourth quadrantregion 114 is the linearly polarized light PL4.

The transmissive light ray group TLG, which comes out of thepolarization modulation element 110, is incident on the lens 120 and iscollected. Thereby, a Z-polarization light component is generated inaddition to the X-polarization light component and Y-polarization lightcomponent. In short, light CL, which is collected by the lens 120,includes the X-polarization light component, Y-polarization lightcomponent and Z-polarization light component. The X-polarization lightcomponent, in this case, is a polarization light component which isparallel to the X direction, the Y-polarization light component is apolarization light component which is parallel to the Y direction, andthe Z-polarization light component is a polarization light componentwhich is parallel to the Z direction.

Each of the transmissive light rays emerging from the first to fourthquadrant regions 111 to 114 includes the X-polarization light componentand Y-polarization light component, which have different phases. Thus,the canceling function due to interference with other transmissive lightrays emerging from the other quadrant regions can be reduced.Preferably, the phases of the transmissive light rays, which have passedthrough the first quadrant region 111, second quadrant region 112, thirdquadrant region 113 and fourth quadrant regions 114, are displaced atequal intervals. For example, a phase difference between thetransmissive light, which has passed through an i-th quadrant region(i=1 to N−1; N is an integer of 4 or more) of the polarizationmodulation element 110, and the transmissive light, which has passedthrough the neighboring (i+1)th quadrant region, should preferably beλ/(4×(N−1)).

FIG. 10 shows a structure example of a polarization control element unit200 which is applicable to an actual exposure device. Specifically, thepolarization control element unit 200 includes, as shown in FIG. 9, apolarization modulation element unit 210 in which polarizationmodulation elements 110 are disposed in a matrix, and a lens array unit220 in which lenses 120 corresponding to the polarization modulationelements 110 are integrated.

The polarization control element unit 200 having this structure isapplied to the exposure steps indicated by “PHOTO1 EXPOSURE” and “PHOTO2EXPOSURE”. Thereby, light can efficiently be absorbed by the firstdopant material EM1 which is included in the red light emission layerEML1 and the second dopant material EM2 which is included in the greenlight emission layer EML2. The reason for this is described below.

Thin films, such as the red light emission layer EML1 and green lightemission layer EML2, which are formed by evaporation methods, haveamorphous structures. Thus, the orientation directions of molecules ofthe first dopant material EM1 and second dopant material EM2, which areincluded in the red light emission layer EML1 and green light emissionlayer EML2, are random.

In some cases, the light absorbance of molecules of the first dopantmaterial EM1 and the second dopant material EM2 greatly varies accordingto directions of polarization. In such cases, it is possible that thethin film of the amorphous structure includes molecules in which theabsorbance for the Z-polarization light component is higher than theabsorbance for the X-polarization light component and Y-polarizationlight component. Thus, in the case of radiating light including only theX-polarization light component and Y-polarization light component, thereis a concern that the exposure time for causing optical quenching in thefirst dopant material EM1 and second dopant material EM2 increases, andthe production efficiency deteriorates.

Thus, in the case where the first dopant material EM1 and second dopantmaterial EM2 include molecules with relatively high absorbance for theX-polarization light component, molecules with relatively highabsorbance for the Y-polarization light component and molecules withrelatively high absorbance for the Z-polarization light component, thelight including the Z-polarization light component, as well as theX-polarization light component and Y-polarization light component, isradiated in the exposure steps indicated by “PHOTO1 EXPOSURE” and“PHOTO2 EXPOSURE”. Thereby, light can efficiently be absorbed in therespective molecules, and the optical quenching can be effected in ashort exposure time. Therefore, the production efficiency can beimproved.

As has been described above, it is possible to provide an organic ELdisplay device, which can effect full-color display with high fineness,without using a fine mask.

The present invention is not limited directly to the above-describedembodiments. In practice, the structural elements can be modified andembodied without departing from the spirit of the invention. Variousinventions can be made by properly combining the structural elementsdisclosed in the embodiments. For example, some structural elements maybe omitted from all the structural elements disclosed in theembodiments. Furthermore, structural elements in different embodimentsmay properly be combined.

In the above-described embodiment, the organic EL display deviceincludes three kinds of organic EL elements with different emissionlight colors, namely, the first to third organic EL elements OLED1 toOLED3. Alternatively, the organic EL display device may include, asorganic EL elements, only two kinds of organic EL elements withdifferent emission light colors, or four or more kinds of organic ELelements with different emission light colors.

In the present embodiment, the description has been given of the case inwhich when the dopant material is in an optical quenching state, nolight is emitted at all from the dopant material. However, if the sameadvantageous effect can be obtained, the invention is applicable to thecase in which when the dopant material is in an optical quenching state,light is hardly emitted from the dopant material.

1. An organic EL display device comprising: a pixel electrode which isdisposed in each of first to third organic EL elements having differentemission light colors; a first light emission layer which includes afirst dopant material having a first absorbance peak in absorbancespectrum characteristics and a first host material having a firstabsorbance bottom on a shorter wavelength side than the first absorbancepeak, the first light emission layer extending over the first to thirdorganic EL elements and being disposed above the pixel electrodes of thefirst to third organic EL elements; a second light emission layer whichincludes a second dopant material having a second absorbance peak inabsorbance spectrum characteristics and a second host material having asecond absorbance bottom on a shorter wavelength side than the firstabsorbance peak and than the second absorbance peak, the second lightemission layer extending over the first to third organic EL elements andbeing disposed above the first light emission layer; a third lightemission layer which includes a third dopant material and a third hostmaterial, the third light emission layer extending over the first tothird organic EL elements and being disposed above the second lightemission layer; and a counter-electrode which extends over the first tothird organic EL elements and is disposed above the third light emissionlayer.
 2. The organic EL display device according to claim 1, whereinthe first dopant material of the second organic EL element is in anoptical quenching state, and the first dopant material and the seconddopant material of the third organic EL element are in an opticalquenching state.
 3. The organic EL display device according to claim 1,wherein the first host material and the second host material have anabsorbance of 10% or less at wavelengths of 350 nm or more in normalizedabsorbance spectrum characteristics thereof.
 4. The organic EL displaydevice according to claim 1, wherein at least one of the first dopantmaterial, the second dopant material and the third dopant material is aphosphorescent material.
 5. An organic EL display device comprising: apixel electrode which is disposed in each of first to third organic ELelements having different emission light colors; a first light emissionlayer which includes a first dopant material having a first absorbancepeak and a first host material having a first absorbance bottom, atwhich a normalized absorbance in normalized absorbance spectrumcharacteristics is 10% or less, on a shorter wavelength side than thefirst absorbance peak, the first light emission layer extending over thefirst to third organic EL elements and being disposed above the pixelelectrodes of the first to third organic EL elements; a second lightemission layer which includes a second dopant material having a secondabsorbance peak and a second host material having a second absorbancebottom, at which a normalized absorbance in normalized absorbancespectrum characteristics is 10% or less, on a shorter wavelength sidethan the first absorbance peak and than the second absorbance peak, thesecond light emission layer extending over the first to third organic ELelements and being disposed above the first light emission layer; athird light emission layer which includes a third dopant material and athird host material, the third light emission layer extending over thefirst to third organic EL elements and being disposed above the secondlight emission layer; and a counter-electrode which extends over thefirst to third organic EL elements and is disposed above the third lightemission layer.
 6. The organic EL display device according to claim 5,wherein the first dopant material of the second organic EL element is inan optical quenching state, and the first dopant material and the seconddopant material of the third organic EL element are in an opticalquenching state.
 7. The organic EL display device according to claim 5,wherein at least one of the first dopant material, the second dopantmaterial and the third dopant material is a phosphorescent material. 8.A manufacturing method of an organic EL display device, comprising: astep of forming a pixel electrode in association with each of first tothird organic EL elements having different emission light colors; a stepof forming above the pixel electrode a first light emission layer byusing a first dopant material having a first absorbance peak inabsorbance spectrum characteristics and a first host material having afirst absorbance bottom on a shorter wavelength side than the firstabsorbance peak, the first light emission layer extending over the firstto third organic EL elements; a step of forming above the first lightemission layer a second light emission layer by using a second dopantmaterial having a second absorbance peak in absorbance spectrumcharacteristics and a second host material having a second absorbancebottom on a shorter wavelength side than the first absorbance peak andthan the second absorbance peak, the second light emission layerextending over the first to third organic EL elements; a step of formingabove the second light emission layer a third light emission layer byusing a third dopant material and a third host material, the third lightemission layer extending over the first to third organic EL elements;and a step of forming above the third light emission layer acounter-electrode which extends over the first to third organic ELelements.
 9. The manufacturing method of an organic EL display device,according to claim 8, further comprising an exposure step of causingoptical quenching in the first dopant material of the second organic ELelement and the third organic EL element, and in the second dopantmaterial of the third organic EL element.
 10. The manufacturing methodof an organic EL display device, according to claim 9, wherein in theexposure step, in a case where a direction of travel of light is set tobe a Z direction and directions perpendicular to each other in a planeperpendicular to the Z direction are set to be an X direction and a Ydirection, light including a polarization light component in the Zdirection, as well as polarization light components in the X directionand Y direction, is radiated.
 11. The manufacturing method of an organicEL display device, according to claim 10, wherein in the exposure step,light is radiated with use of a polarization control element which isconstructed by combining a polarization modulation element whichgenerates, from radiation light from a light source, linearly polarizedlight rays in a plurality of different directions in an X-Y plane, and alens which collects the linearly polarized light rays coming out of thepolarization modulation element.
 12. The manufacturing method of anorganic EL display device, according to claim 11, wherein thepolarization modulation element is a liquid crystal panel.
 13. Themanufacturing method of an organic EL display device, according to claim11, wherein the polarization modulation element includes at least fourquadrant regions which vary a polarization state of the radiation lightfrom the light source, and transmissive light rays emerging from therespective quadrant regions have different phases.
 14. The manufacturingmethod of an organic EL display device, according to claim 13, wherein aphase difference between light coming out of an i-th quadrant region(i=1 to N−1; N is an integer of 4 or more) of the polarizationmodulation element, and light coming out of a neighboring (i+1)thquadrant region, is λ/(4×(N−1)).